You have two areas to check: PC resources and the PSU. If you've over-taxed your system resources, sooner or later it will bite you in any way that inconvietant to you. If the PSU is lacking, it will start to falter, know full details of your needs and what your PSU specs are.. HEAT, is the biggest concern during stable game playing and if not taken care of will effect your whole PC. The PSU and GPU are big sources of heat. You stated you have 1 case fan, it appears that isn't enough. Cool your PC better, check results. Please review the many posts here on this forum and search these forums for any tips, hints and clues on similar posts as yours.
I'm having an issue where my PC will randomly shut down completely during the middle of playing Rift. It is not during particularly intense situations either... Specs below
PSU: CoolerMaster Extreme Power Plus 550W (RS-550-PCAR)
CPU: Intel Core i5 2400
Mobo: AsRock H61M-VS
HDD: 1x Seagate Barracuda 300gb @ 7200rpm, 2x 320gb WD @ 7200rpm
Video: ATI Radeon 5670 512DDR5
RAM: 2x g.skill 2gb ddr3 1333
I've got a dvdrw combo drive and 1 case fan. There is also a 1tb WD external HD plugged in via USB with no external power source...could this be the issue??
I'm fairly certain the 550W should be enough power, but I'm also fairly certain it is the cause of my problem!